tools/nolibc: fix build of the test case using glibc

Some extra tests for various integer types and limits were added by
commit d1209597 ("tools/nolibc: add tests for the integer limits
in stdint.h"), but we forgot to retest with glibc. Stddef and stdint
are now needed for the program to build there.

Cc: Vincent Dagonneau <v@vda.io>
Signed-off-by: Willy Tarreau <w@1wt.eu>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>